/Engine/Source/Runtime/Engine/Classes/Engine/GameInstance.h
Handle a game specific net control message (NMT_GameSpecific) this allows games to insert their own logic into the control channel the meaning of both data parameters is game-specific
virtual void HandleGameNetControlMessage ( class [UNetConnection](API\Runtime\Engine\Engine\UNetConnection) * Connection, uint8 MessageByte, const [FString](API\Runtime\Core\Containers\FString) & MessageStr )